Heavy-ion beams are very suitable for deeply-seated cancer treatment not only owing to their high dose localization around the Bragg peak, but also owing to the high biological effect there. NIRS, therefore, constructed HIMAC as the world’s first heavy-ion accelerator facility dedicated to medical use. NIRS has conducted the cancer treatment with a carbon-ion beam of HIMAC since 1994, which results in the treated patient number of more than 9000 during 20 years operation. Since the carbon-ion radiotherapy with HIMAC was approved as an advanced medical technology in Japan in 2003, NIRS developed a compact carbon-ion radiotherapy facility in order to boost applications of the carbon-ion radiotherapy in Japan. As the fruits of this work, its pilot facility was constructed in the Gunma University, which has been successfully conducted since 2010. NIRS, further, has been engaged in a “new treatment research project” since 2006 for the further development of HIMAC treatments. Toward the adaptive cancer radiotherapy, this project has developed a 3D pencil-beam re-scanning for both the static and moving tumor treatments. The new treatment research facility was constructed in order to apply the technology developed in this project to both the clinical study and treatments. The facility, which is connected with the existing HIMAC accelerator complex, has three treatment rooms: two rooms equipped with both horizontal and vertical beam delivery systems, while one room with a rotating gantry. As the first stage, one of the treatment rooms has been opened with the pencil-beam 3D scanning since May 2011, utilizing an energy degrader for slice change. As the second stage, the second room has been also operated since September 2012 utilizing the hybrid energy scanning with eleven energy steps of the synchrotron for more accurately treatment. The respiratory-gated 3D rescanning with the pencil-beam has been applied since March 2014. As the third stage, a compact heavy-ion rotating gantry for the third room has been developed with the superconducting technology toward the completion in this year. We report the development of HIMAC for the heavy-ion cancer radiotherapy in Japan.International conference on magnet technology 24 (MT 24)